Update actions/checkout action to v6 (#291)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/build.yml

@@ -8,7 +8,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Gradle Wrapper Validation
         uses: gradle/actions/wrapper-validation@v5

.github/workflows/publish-release.yml

@@ -13,7 +13,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Install JDK 11
         uses: actions/setup-java@v5

.github/workflows/publish-snapshot.yml

@@ -13,7 +13,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Install JDK 11
         uses: actions/setup-java@v5